Ceramic electronic device and manufacturing method of the same

ABSTRACT

A ceramic electronic device includes, a multilayer chip in which each of a plurality of dielectric layers and each of a plurality of internal electrode layers are alternately stacked, external electrodes provided on the first end face and the second end face, and a water repellent agent formed on a surface of the external electrodes. A thickness A (&gt;0) of the water repellent agent on at least one of four faces of the external electrodes that cover an upper face in a stacking direction, a lower face in the stacking direction, and two side faces of the multilayer chip is larger than a thickness B (&gt;0) of the water repellent agent on faces of the external electrodes that cover the first end face and the second end face.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application Publication No. 2019-208881, filed onNov. 19, 2019, the entire contents of which are incorporated herein byreference.

FIELD

A certain aspect of the present invention relates to a ceramicelectronic device and a manufacturing method of the ceramic electronicdevice.

BACKGROUND

Since electronic devices are downsized and thicknesses of the electronicdevices are reduced, downsizing and thickness reduction of ceramicelectronic devices are required. The ceramic electronic devices are usedfor various electronic devices. Therefore, usage under variousconditions of the ceramic electronic devices is required. As an example,the ceramic electronic devices are used under a high temperature and ahigh humidity. However, when the ceramic electronic devices are usedunder the high temperature and the high humidity, water adheres to asurface of the ceramic electronic devices because of dew condensation.And, electrical breakdown may occur. And so, there is discloses atechnology in which a water repellent agent is provided on the surfaceof the ceramic electronic devices by surface treatment (for example, seeJapanese Patent Application Publication No. 2015-115392).

SUMMARY OF THE INVENTION

However, in the technology, it is necessary to remove the waterrepellent agent of a surface of external electrodes, before mounting ofthe ceramic electronic devices, in order to prevent mounting failure.

According to an aspect of the present invention, there is provided aceramic electronic device including: a multilayer chip in which each ofa plurality of dielectric layers and each of a plurality of internalelectrode layers are alternately stacked, a main component of thedielectric layers being ceramic, the multilayer chip having arectangular parallelepiped shape, the plurality of internal electrodelayers being exposed to at least one of a first end face and a secondend face of the multilayer structure, the first end face facing with thesecond end face; external electrodes provided on the first end face andthe second end face; and a water repellent agent formed on a surface ofthe external electrodes, wherein a thickness A (>0) of the waterrepellent agent on at least one of four faces of the external electrodesthat cover an upper face in a stacking direction, a lower face in thestacking direction, and two side faces of the multilayer chip is largerthan a thickness B (>0) of the water repellent agent on faces of theexternal electrodes that cover the first end face and the second endface.

According to another aspect of the present invention, there is provideda manufacturing method of a ceramic electronic device including:preparing a ceramic electronic device having a multilayer chip, andexternal electrodes; and forming an water repellent agent on a surfaceof the external electrodes; wherein the multilayer chip has a structurein which each of a plurality of dielectric layers and each of aplurality of internal electrode layers are alternately stacked, a maincomponent of the dielectric layers being ceramic, the multilayer chiphaving a rectangular parallelepiped shape, the plurality of internalelectrode layers being exposed to at least one of a first end face and asecond end face of the multilayer chip, the first end face facing withthe second end face, the external electrodes being provided on the firstend face and the second end face, wherein a thickness A (>0) of thewater repellent agent on at least one of four faces of the externalelectrodes that cover an upper face in a stacking direction, a lowerface in the stacking direction, and two side faces of the multilayerchip is larger than a thickness B (>0) of the water repellent agent onfaces of the external electrodes that cover the first end face and thesecond end face.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a multilayer ceramic capacitorin which a cross section of a part of the multilayer ceramic capacitoris illustrated;

FIG. 2 illustrates a cross sectional view of an external electrode andis a partial cross sectional view taken along a line A-A of FIG. 1;

FIG. 3A and FIG. 3B illustrate an outer circumference of externalelectrodes and edge faces external electrodes;

FIG. 4 illustrates a structure in which a multilayer ceramic capacitoris mounted on a circuit substrate;

FIG. 5A and FIG. 5B illustrate an XPS depth analysis;

FIG. 6 illustrates measurement of a water repellent agent;

FIG. 7 illustrates a manufacturing method of a multilayer ceramiccapacitor; and

FIG. 8 illustrates a manufacturing method of a multilayer ceramiccapacitor.

DETAILED DESCRIPTION

A description will be given of an embodiment with reference to theaccompanying drawings.

(Embodiment) A description will be given of an outline of a multilayerceramic capacitor. FIG. 1 illustrates a perspective view of a multilayerceramic capacitor 100 in accordance with an embodiment, in which a crosssection of a part of the multilayer ceramic capacitor 100 isillustrated. As illustrated in FIG. 1, the multilayer ceramic capacitor100 includes a multilayer chip 10 having a rectangular parallelepipedshape, and a pair of external electrodes 20 a and 20 b that arerespectively provided at two end faces of the multilayer chip 10 facingeach other. In four faces other than the two end faces of the multilayerchip 10, two faces other than an upper face and a lower face of themultilayer chip 10 in a stacking direction are referred to as sidefaces. The external electrodes 20 a and 20 b extend to the upper face,the lower face and the two side faces of the multilayer chip 10.However, the external electrodes 20 a and 20 b are spaced from eachother. Therefore, at least a part of each of the upper face, the lowerface and the two side faces of the multilayer chip 10 is not covered bythe external electrodes 20 a and 20 b and is exposed to atmosphere.

The multilayer chip 10 has a structure designed to have dielectriclayers 11 and internal electrode layers 12 alternately stacked. Thedielectric layer 11 includes ceramic material acting as a dielectricmaterial. The internal electrode layers 12 include a base metalmaterial. End edges of the internal electrode layers 12 are alternatelyexposed to a first end face of the multilayer chip 10 and a second endface of the multilayer chip 10 that is different from the first endface. In the embodiment, the first end face faces with the second endface. The external electrode 20 a is provided on the first end face. Theexternal electrode 20 b is provided on the second end face. Thus, theinternal electrode layers 12 are alternately conducted to the externalelectrode 20 a and the external electrode 20 b. Thus, the multilayerceramic capacitor 100 has a structure in which a plurality of dielectriclayers 11 are stacked and each two of the dielectric layers 11 sandwichthe internal electrode layer 12. In a multilayer structure of thedielectric layers 11 and the internal electrode layers 12, the internalelectrode layer 12 is positioned at an outermost layer in a stackingdirection. The upper face and the lower face of the multilayer structurethat are the internal electrode layers 12 are covered by cover layers13. A main component of the cover layer 13 is a ceramic material. Forexample, a main component of the cover layer 13 is the same as that ofthe dielectric layer 11.

For example, the multilayer ceramic capacitor 100 may have a length of0.25 mm, a width of 0.125 mm and a height of 0.125 mm. The multilayerceramic capacitor 100 may have a length of 0.4 mm, a width of 0.2 mm anda height of 0.2 mm. The multilayer ceramic capacitor 100 may have alength of 0.6 mm, a width of 0.3 mm and a height of 0.3 mm. Themultilayer ceramic capacitor 100 may have a length of 1.0 mm, a width of0.5 mm and a height of 0.5 mm. The multilayer ceramic capacitor 100 mayhave a length of 3.2 mm, a width of 1.6 mm and a height of 1.6 mm. Themultilayer ceramic capacitor 100 may have a length of 4.5 mm, a width of3.2 mm and a height of 2.5 mm. However, the size of the multilayerceramic capacitor 100 is not limited.

A main component of the internal electrode layers 12 is a base metalsuch as nickel (Ni), copper (Cu), tin (Sn) or the like. The internalelectrode layers 12 may be made of a noble metal such as platinum (Pt),palladium (Pd), silver (Ag), gold (Au) or alloy thereof. The dielectriclayers 11 are mainly composed of a ceramic material that is expressed bya general formula ABO₃ and has a perovskite structure. The perovskitestructure includes ABO_(3-α) having an off-stoichiometric composition.For example, the ceramic material is such as BaTiO₃ (barium titanate),CaZrO₃ (calcium zirconate), CaTiO₃ (calcium titanate), SrTiO₃ (strontiumtitanate), Ba_(1-x-y)Ca_(x)Sr_(y)Ti_(1-z)Zr_(z)O₃ (0≤x≤1, 0≤y≤1, 0≤z≤1)having a perovskite structure.

FIG. 2 illustrates a cross sectional view of the external electrode 20 band is a partial cross sectional view taken along a line A-A of FIG. 1.In FIG. 2, hatching for cross section is omitted. As illustrated in FIG.2, the external electrode 20 b has a structure in which a first platedlayer 22 such as Cu, a conductive resin layer 23, a second plated layer24 such as Ni and a third plated layer 25 such as Sn are formed on abase layer 21 in this order. The base layer 21, the first plated layer22, the conductive resin layer 23, the second plated layer 24 and thethird plated layer 25 extend toward the upper face, the lower face, andthe two side faces of the multilayer chip 10 from the both end faces ofthe multilayer chip 10.

A main component of the base layer 21 is a metal such as Cu, Ni, Al(aluminum) or Zn (zinc). The base layer 21 includes a glass componentfor densifying the base layer 21 or a co-material for controllingsinterability of the base layer 21. The base layer 21 including theseceramic components has high adhesiveness with the cover layer 13 whosemain component is a ceramic material. The conductive resin layer 23 is aresin layer including a metal component such as Ag. The conductive resinlayer 23 is flexible. Therefore, the conductive resin layer 23suppresses stress caused by deflection of a substrate on which themultilayer ceramic capacitor 100 is mounted. The first plated layer 22is provided in order to increase adhesiveness between the base layer 21and the conductive resin layer 23. The external electrode 20 a has thesame structure as the external electrode 20 b. The conductive resinlayer 23 may not be necessarily provided.

When the external electrodes 20 a and 20 b have the structureillustrated in FIG. 2 and the multilayer ceramic capacitor 100 is usedin high-temperature and high-humidity condition, a metal component ofthe conductive resin layer 23 may diffuse because of water adhered tothe surface of the multilayer ceramic capacitor 100. In this case,reliability of the multilayer ceramic capacitor 100 may be degraded. Forexample, the metal component of the conductive resin layer 23 maydiffuse to the surface of the multilayer chip 10 between the externalelectrode 20 a and the external electrode 20 b (migration phenomena).Even if the external electrodes 20 a and 20 b do not include theconductive resin layer 23, another metal component of the externalelectrodes 20 a and 20 b may diffuse.

And so, the multilayer ceramic capacitor 100 of the embodiment has astructure in which a water repellent agent is provided on a surface ofthe external electrode 20 a and 20 b.

A description will be given of each part of the surface of the externalelectrodes 20 a and 20 b. As illustrated in FIG. 3A, four faces of eachof the external electrodes 20 a and 20 b are referred to as an outercircumference of the external electrode (outer circumference 26). Theouter circumference 26 covers a part of the upper face, a part of thelower face, and a part of the two side faces of the multilayer chip 10.A face of each of the external electrodes 20 a and 20 b covering each ofthe edge faces of the multilayer chip 10 is referred to as an edge faceof the external electrode (an edge face 27). In concrete, as illustratedin FIG. 3B, when the multilayer ceramic capacitor 100 is seen from theside face thereof, the edge faces 27 of the external electrodes 20 a and20 b are between a straight line obtained by extending the upper face ofthe multilayer chip 10 to the sides of the external electrodes 20 a and20 b and a straight line obtained by extending the lower face of themultilayer chip 10 to the sides of the external electrodes 20 a and 20b. And, the rest exposed surfaces of the external electrodes 20 a and 20b are the outer circumferences 26.

In the multilayer ceramic capacitor 100 of the embodiment, a waterrepellent agent 30 is provided on the surface of the external electrodes20 a and 20 b, as illustrated in FIG. 2. The water repellent agent 30may be provided on an exposed surface of the multilayer chip 10 wherethe external electrodes 20 a and 20 b are not provided. A thickness ofthe water repellent agent 30 on the outer circumferences 26 of theexternal electrode 20 a and 20 b is a thickness A. A thickness of thewater repellent agent 30 on the edge faces 27 is a thickness B. Arelationship “thickness A>thickness B” is satisfied. The thickness ismeasured by an analysis method such as XPS (X-ray PhotoelectronSpectroscopy).

The water repellent agent 30 is formed on the outer circumference 26.Therefore, adhesion of water on the surface of the outer circumference26 is suppressed. It is therefore possible to suppress the connectionbetween the external electrode 20 a and the external electrode 20 bcaused by water. Accordingly, it is possible to suppress breakdown ofthe multilayer ceramic capacitor 100 caused by migration caused by thedew condensation.

The thickness B of the water repellent agent 30 on the edge face 27 issmaller than the thickness A of the water repellent agent 30 on theouter circumference 26. Therefore, the water repellent agent 30 on theedge face 27 is thin. In this case, the influence of the water repellentagent 30 on the edge face 27 is small. And, the solder crawls to theedge face 27. Therefore, solder bonding can be achieved. And mountingfailure can be suppressed. FIG. 4 illustrates a structure in which themultilayer ceramic capacitor 100 is mounted on a circuit substrate 201.When the influence of the water repellent agent 30 on the edge face 27is small, a solder 202 crawls to the edge face 27, as illustrated inFIG. 4.

In the embodiment, the relationship “the thickness A of the waterrepellent agent 30 on the outer circumference 26>the thickness B of thewater repellent agent 30 on the edge face 27” is satisfied. It istherefore possible to suppress the mounting failure, even if the waterrepellent agent 30 is not removed.

When the water repellent agent 30 on the outer circumference 26 isexcessively thin, adhesion of water on the outer circumference 26 maynot be necessarily suppressed. And so, it is preferable that thethickness A of the water repellent agent 30 on the outer circumferencehas a lower limit. For example, it is preferable that the thickness A ofthe water repellent agent 30 on the outer circumference 26 is 10 nm ormore. It is more preferable that the thickness A is 20 nm or more. It isstill more preferable that the thickness A is 40 nm or more.

When the water repellent agent 30 on the outer circumference 26 isexcessively thick, wettability of the solder with respect to theexternal electrodes 20 a and 20 b is degraded during mounting of themultilayer ceramic capacitor 100. And mounting failure may occur. Andso, it is preferable that the thickness A of the water repellent agent30 on the outer circumference 26 has an upper limit. For example, it ispreferable that the thickness A of the water repellent agent 30 on theouter circumference 26 is 100 nm or less. It is more preferable that thethickness A is 60 nm or less.

When the water repellent agent 30 on the edge face 27 is excessivelythick, the influence of the water repellent agent 30 is large. Thewettability of the solder with respect to the external electrodes 20 aand 20 b may be degraded during mounting of the multilayer ceramiccapacitor 100. And the mounting failure may occur. And so, it ispreferable that the thickness B of the water repellent agent 30 on theedge face 27 has an upper limit. For example, it is preferable that thethickness B of the water repellent agent 30 on the edge face 27 is 50 nmor less. It is more preferable that the thickness B is 20 nm or less. Itis still more preferable that the thickness B is 15 nm or less.

When the water repellent agent 30 is also provided on the exposedsurfaces of the upper face, the lower face, and the two side faces ofthe multilayer chip 10 where the external electrodes 20 a and 20 b arenot provided, the adhesion of water to the exposed surfaces of themultilayer chip 10 is suppressed. And, the breakdown caused by themigration due to the dew condensation can be suppressed.

The embodiment achieves remarkable effect in the multilayer ceramiccapacitor which has the external electrode having the conductive resinlayer 23 including grains such as silver causing the migration.

The material of the water repellent agent 30 is not limited when acontact angle of the material with respect to water is 90 degrees ormore. The water repellent agent 30 is, for example, a silicon-basedmaterial. As the silicon-based material, organic compound having asiloxane bonding can be used. For example, the organic compound havingthe siloxane bonding is a small molecule cyclic siloxane which is acyclic siloxane from D3 to D20. For example, the small molecule cyclicsiloxane D3 is trimer of the cyclic siloxane which is a solid substanceof hexamethyl cyclotrisiloxane (C₆H₁₈O₃Si₃). The small molecule cyclicsiloxane D4 is tetramer of the cyclic siloxane which is semi-solidsubstance of octamethyl cyclotetrasiloxane (C₈H₂₄O₄Si₄). The organiccompound having the siloxane bonding releases the small molecule cyclicsiloxane Dn (n≥3) at a relatively high temperature. Therefore, theorganic compound having the siloxane bonding tends to be left aftermounting the multilayer ceramic capacitor 100 with solder.

Alternatively, as the material of the water repellent agent 30,fluorine-based material can be used.

A description will be given of a measuring method of the water repellentagent 30. For example, an XPS (X-ray Photoelectron Spectroscopy) depthanalysis can be used as the measuring method of the water repellentagent 30. With the XPS depth analysis, it is possible to measurecomponent distribution in a depth direction. In concrete, a surface of asample is scraped in a depth direction by sputtering using argon ion(Ar⁺). As illustrated in FIG. 5, a concentration of a surface componentis detected. Further, the surface of the sample is scraped. And aconcentration of a surface component is detected. The process isrepeated. Thus, as illustrated in FIG. 5B, a relationship between anaccumulated time of the sputtering and a concentration of a detectedcomponent can be measured. The accumulated time of the sputtering can beconverted into a thickness. It is therefore possible to measure thethickness of the water repellent agent 30.

For example, as illustrated in FIG. 6, a primary correlation line isdrawn on the basis of a plurality of plots between the thickness of thewater repellent agent 30 and the component of the water repellent agent30 (except for abnormal values). The accumulated time of the sputteringat which the concentration is zero (an intersection with the X axis) canbe converted into the thickness of the water repellent agent 30.

Next, a description will be given of a manufacturing method of themultilayer ceramic capacitor 100. FIG. 7 illustrates a manufacturingmethod of the multilayer ceramic capacitor 100.

(Making process of raw material powder)(S1) A dielectric material forforming the dielectric layer 11 is prepared. Generally, an A siteelement and a B site element are included in the dielectric layer 11 ina sintered phase of grains of ABO₃. For example, BaTiO₃ is tetragonalcompound having a perovskite structure and has a high dielectricconstant. Generally, BaTiO3 is obtained by reacting a titanium materialsuch as titanium dioxide with a barium material such as barium carbonateand synthesizing barium titanate. Various methods can be used as asynthesizing method of the ceramic structuring the dielectric layer 11.For example, a solid-phase method, a sol-gel method, a hydrothermalmethod or the like can be used. The embodiment may use any of thesemethods.

An additive compound may be added to resulting ceramic powders, inaccordance with purposes. The additive compound may be an oxide of Mg(magnesium), Mn (manganese), V (vanadium), Cr (chromium) or a rare earthelement (Y (yttrium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb(terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium) andYb (ytterbium)), or an oxide of Co (cobalt), Ni, Li (lithium), B(boron), Na (sodium), K (potassium) and Si, or glass.

In the embodiment, it is preferable that ceramic particles structuringthe dielectric layer 11 are mixed with compound including additives andare calcined in a temperature range from 820 degrees C. to 1150 degreesC. Next, the resulting ceramic particles are wet-blended with additives,are dried and crushed. Thus, ceramic powder is obtained. For example, itis preferable that an average grain diameter of the resulting ceramicpowder is 50 nm to 300 nm from a viewpoint of thickness reduction of thedielectric layer 11. The grain diameter may be adjusted by crushing theresulting ceramic powder as needed. Alternatively, the grain diameter ofthe resulting ceramic power may be adjusted by combining the crushingand classifying.

(Stacking process)(S2) Next, a binder such as polyvinyl butyral (PVB)resin, an organic solvent such as ethanol or toluene, and a plasticizerare added to the resulting dielectric material and wet-blended. With useof the resulting slurry, a strip-shaped dielectric green sheet with athickness of 0.8 μm or less is coated on a base material by, forexample, a die coater method or a doctor blade method, and then dried.

Next, metal conductive paste for forming an internal electrode isapplied to the surface of the dielectric green sheet by screen printingor gravure printing. The metal conductive paste includes an organicbinder. Thus, a pattern for forming an internal electrode layer isprovided. As co-materials, ceramic particles are added to the metalconductive paste. A main component of the ceramic particles is notlimited. However, it is preferable that the main component of theceramic particles is the same as that of the dielectric layer 11.

Then, the dielectric green sheets are alternately stacked while the basematerial is peeled so that the internal electrode layers 12 and thedielectric layers 11 are alternated with each other and the end edges ofthe internal electrode layers 12 are alternately exposed to both endfaces in the length direction of the dielectric layer 11 so as to bealternately led out to the pair of external electrodes 20 a and 20 b ofdifferent polarizations. For example, a total number of the stakeddielectric green sheets is 100 to 500.

After that, a cover sheet to be the cover layer 13 is cramped on themultilayer structure of the dielectric green sheets. And another coversheet to be the cover layer 13 is cramped under the multilayerstructure. Thus, a ceramic multilayer structure is obtained. After that,the binder is removed from the ceramic multilayer structure (forexample, 1.0 mm×0.5 mm) in N₂ atmosphere of 250 degrees C. to 500degrees C.

(Firing process)(S3) The resulting compact is fired for ten minutes to 2hours in a reductive atmosphere having an oxygen partial pressure of10⁻⁷ to 10⁻¹⁰ atm in a temperature range of 1100 degrees C. to 1300degrees C. In this manner, it is possible to manufacture the multilayerceramic capacitor 100.

(Re-oxidizing process)(S4) After that, a re-oxidizing process may beperformed in N₂ gas atmosphere in a temperature range of 600 degrees C.to 1000 degrees C.

(Forming process of external electrodes)(S5) Metal paste including ametal filler, a glass frit, a binder and a solvent is applied to theboth end faces of the multilayer chip 10 by dipping, and is dried. Afterthat, the metal paste is baked. Thus, the base layer 21 is formed. Thebinder and the solvent vaporize by the baking. In the method, it ispreferable that the metal filler is Cu or the like. It is preferablethat the baking is performed for 3 minutes to 30 minutes in atemperature range of 700 degrees C. to 900 degrees C. It is morepreferable that the baking is performed for 5 minutes to 15 minutes in atemperature range of 760 degrees C. to 840 degrees C. After that, thefirst plated layer 22 may be formed on the base layer 21 by plating.

Next, the conductive resin layer 23 is formed. For example, theconductive resin layer 23 is formed by immersion-coating thermosettingresin such as epoxy resin or phenol resin in which conductive fillerssuch as Ag, Ni, Cu or the like are kneaded, on the surface of the firstplated layer 22, and hardening the thermosetting resin by thermaltreatment. The thickness of the conductive resin layer 23 is notlimited. For example, the thickness of the conductive resin layer 23 isapproximately 10 μm to 50 μm. The thickness of the conductive resinlayer 23 may be determined in accordance with the size of the multilayerceramic capacitor 100. After that, the second plated layer 24 and thethird plated layer 25 are formed on the conductive resin layer 23 byelectroplating or the like.

(Contact heating process)(S6) When the silicon-based material is used asthe water repellent agent 30, silicon rubber is heated to 120 degrees C.or more and is contacted to the surface of the multilayer ceramiccapacitor 100 after covering a region of the multilayer ceramiccapacitor 100 other than a region on which the water repellent agent 30is to be formed, with a mask. For example, when a mask covers a part ofeach of the external electrodes 20 a and 20 b which is other than theouter circumference 26, it is possible to selectively form the waterrepellent agent 30 on the outer circumference 26. Similarly, whenanother mask covers a part of each of the external electrodes 20 a and20 b which is other than the edge face 27, it is possible to selectivelyform the water repellent agent 30 on the edge face 27. When another maskcovers a part of the multilayer chip 10 which is other than the exposedregion of the multilayer chip 10, it is possible to selectively form thewater repellent agent 30 on the exposed region of the multilayer chip10. The water repellent agent 30 becomes thicker, when the temperatureof the heated silicon rubber and the heated fluorine rubber is increasedand the number of the heating is increased. With the conditions, it ispossible to adjust the thickness of the water repellent agent 30. Thefluorine rubber is heated to 150 degrees C. or more, a surface of themultilayer ceramic capacitor 100 other than a region where the waterrepellent agent 30 is to be formed is covered by a mask, and thefluorine rubber contacts to the surface of the multilayer ceramiccapacitor 100, when the fluorine-based material is used as the waterrepellent agent 30. Thus, the water repellent agent 30 is formed.

With the manufacturing method of the embodiment, the water repellentagent 30 is formed so that the relationship “the thickness A of thewater repellent agent 30 of the outer circumference 26>the thickness Bof the water repellent agent 30 on the edge face 27” is satisfied. Inthis case, it is possible to suppress the mounting failure even if thewater repellent agent 30 is not removed.

When the silicon rubber is heated to 120 degrees C. or more and iscontacted to the surface of the multilayer ceramic capacitor 100, thetemperature at which the small molecule cyclic siloxane Dn (n≥3) isreleased from the water repellent agent 30 is 300 degrees C. or more.Therefore, a sufficient large amount of the water repellent agent 30 canbe left, after mounting the multilayer ceramic capacitor 100 withsolder.

The fluorine-based material which is not released from the surface ofthe multilayer ceramic capacitor 100 at a temperature of less than 380degrees C. and is released from the surface of the multilayer ceramiccapacitor 100 at a temperature of 380 degrees C. or more is adhered tothe surface of the multilayer ceramic capacitor 100. Therefore, asufficient large amount of the water repellent agent 30 can be left,after mounting the multilayer ceramic capacitor 100 with solder.

The base layer 21 may be fired together with the multilayer chip 10. Inthis case, as illustrated in FIG. 8, the binder is removed from theceramic multilayer structure in N₂ atmosphere of 250 degrees C. to 500degrees C. After that, metal paste including a metal filler, aco-material, a binder and a solvent is coated on the both end faces ofthe ceramic multilayer structure by a dipping method or the like and isdried (S3). After that, the metal paste is fired together with theceramic multilayer structure (S4). Firing condition is described in theabove-mentioned firing process. After that, a re-oxidizing process maybe performed in N2 gas atmosphere in a temperature range of 600 degreesC. to 1000 degrees C. (S5). After that, the first plated layer 22 isformed on the base layer 21 by plating. Next, the conductive resin layer23 is formed on the first plated layer 22. After that, the second platedlayer 24 and the third plated layer 25 are formed on the conductiveresin layer 23 by electroplating or the like.

In the embodiment, the thicknesses A of the water repellent agent 30 ofall of the four faces of the outer circumference 26 are larger than thethickness B of the water repellent agent 30 of the edge face 27.However, the structure is not limited. For example, the thickness A ofthe water repellent agent 30 of at least one of the four faces is largerthan the thickness B of the water repellent agent 30 of the edge face27.

In the embodiment, the water repellent agent 30 is provided on the edgeface 27. However, the water repellent agent 30 may not be necessarilyprovided on the edge face 27. Therefore, the thickness A of the waterrepellent agent 30 on the outer circumference 26 is more than 0 nm. And,the thickness B of the water repellent agent 30 on the edge face 27 is 0nm or more.

In the embodiments, the multilayer ceramic capacitor is described as anexample of ceramic electronic devices. However, the embodiments are notlimited to the multilayer ceramic capacitor. For example, theembodiments may be applied to another electronic device such as varistoror thermistor.

EXAMPLES

The multilayer ceramic capacitors in accordance with the embodiment weremade and the property was measured.

(Examples 1 to 4 and comparative examples 1 and 2) An organic binder waskneaded with ceramic powder, of which a main component was bariumtitanate, having reduction resistant. Thus, slurry was prepared. Theslurry was formed into a sheet by doctor blade. Thus, a dielectric greensheet was made. Metal conductive paste of Ni having a predeterminedpattern was applied to the dielectric green sheet by screen printing.Thus, an internal electrode pattern was formed. The dielectric greensheet on which the internal electrode pattern was formed was stampedinto a predetermined size. And a predetermined number of the dielectricgreen sheets were stacked. And a ceramic multilayer structure was madeby thermos-compression.

Next, the ceramic multilayer structure was cut into predetermined chipsizes and was divided. Metal paste including a co-material was appliedto the both end faces of the ceramic multilayer structure (faces exposedto external electrodes) by an immersion method so that the metal pastehas a predetermined electrode width (E size).

Next, the resulting ceramic multilayer structure was fired at a 1250degrees C. in nitrogen or hydrogen atmosphere and was subjected to apredetermined thermal treatment. Thus, the base layer 21 covering themultilayer chip 10 and the both end faces of the multilayer chip 10 wasmade. Next, the surface of the base layer 21 was subjected to drypolishing with use of “whitemorundum” (registered trademark) as apolishing agent. After that, the first plated layer 22 was formed byCu-plating. Next, conductive resin paste of which viscosity was adjustedto a predetermined value (10 to 30 Pa·s) was applied to the surface ofthe first plated layer 22 by an immersion method. Epoxy resin in whichan Ag filler was kneaded was used as the conductive resin paste. Afterthat, the conductive resin layer 23 was formed by hardening theconductive resin paste by a thermal treatment. And, the second platedlayer 24 and the third plated layer 25 were formed on the conductiveresin layer 23 by Ni-plating and Sn-plating. The resulting multilayerceramic capacitor 100 had a length of 3.2 mm, a width of 2.5 mm and aheight of 2.5 mm. The distance between the external electrode 20 a andthe external electrode 20 b was 1.6 mm.

The multilayer ceramic capacitors 100 were fixed to a jig. The regionsother than the regions where the water repellent agent 30 were to beformed were masked. Fluorine rubber was contacted to the surfaces of themultilayer ceramic capacitors 100. Thus, the water repellent agent 30was selectively formed on the regions which were not masked. In theexample 1, the thickness of the water repellent agent 30 on the outercircumference was 9.32 nm. And the thickness of the water repellentagent 30 on the edge face 27 was 2.79 nm. In the example 2, thethickness of the water repellent agent 30 on the outer circumference was19.26 nm. And the thickness of the water repellent agent 30 on the edgeface 27 was 4.65 nm. In the example 3, the thickness of the waterrepellent agent 30 on the outer circumference was 32.95 nm. And thethickness of the water repellent agent 30 on the edge face 27 was 7.71nm. In the example 4, the thickness of the water repellent agent 30 onthe outer circumference was 48.66 nm. And the thickness of the waterrepellent agent 30 on the edge face 27 was 10.15 nm. In the comparativeexample 1, the water repellent agent 30 was formed on neither the outercircumference 26 nor the edge face 27. In the comparative example 2, thethickness of the water repellent agent 30 on the outer circumference was18.69 nm. And the thickness of the water repellent agent 30 on the edgeface 27 was 52.46 nm.

Next, other 200 samples were subjected to a dew condensation test, withrespect to each of the examples 1 to 4 and the comparative examples 1and 2. The samples were mounted on reliable substrates (CEM 3). Thesamples were put in a thermo-hygrostat tank. And, 16 V was applied tothe samples. A dew condensation test program of JIS 60068-2-30 wasperformed 6 times. After that, it was confirmed whether the migrationoccurred or not. The condition of each cycle of the program is asfollows. (1) The humidity was kept at 98%. The temperature was changedfrom 25 degrees C. to 55 degrees C. for 3 hours. (2) The temperature waskept at 55 degrees C. The humidity was changed from 98% to 93% for 15minutes. (3) The temperature was kept at 55 degrees C. and the humiditywas kept at 93% for 9 hours and 25 minutes. (4) The humidity was kept at93%. The temperature was changed from 55 degrees C. to 25 degrees C. forthree hours. (5) The temperature was kept at 25 degrees C. and thehumidity was kept at 93% for 3 hours. (6) The temperature was kept at 25degrees C. The humidity was changed from 93% to 98% for 5 hours and 30minutes. Each sample was observed by a stereomicroscope of 40magnifications. And it was determined whether there was a precipitatebetween external electrodes. When there was a precipitate, it wasdetermined that the migration occurred.

200 samples were subjected to a mounting test, with respect to each ofthe examples 1 to 4 and the comparative examples 1 and 2. In themounting test, a reflow furnace of which a maximum temperature was 270degrees C. or more was used. And, an external view was observed withrespect to each sample. When the crawling angle of the edge of thesolder fillet was less than 90 degrees with respect to the edge face ofthe external electrode, it was determined as acceptance. When thecrawling angle was 90 degrees or more, it was determined asnon-acceptance.

Table shows the results. As shown in Table 1, all samples of theexamples 1 to 4 were determined as good in the dew condensation test. Itis thought that this was because the water repellent agent 30 was formedon the outer circumference 26. All samples of the comparative example 2were determined as good in the dew condensation test. It is thought thatthis was because the water repellent agent 30 was formed on the outercircumference 26. However, in the comparative example 1, 12 samplesamong 200 samples were determined as bad in the dew condensation test.It is thought that this was because the water repellent agent 30 was notformed on the outer circumference 26.

TABLE 1 EXAMPLE EXAMPLE EXAMPLE EXAMPLE COMPARATIVE COMPARATIVE 1 2 3 4EXAMPLE 1 EXAMPLE 2 THICKNESS 9.32 19.26 32.95 48.66 0 18.69 OF OUTERCIRCUMFERENCE [nm] THICKNESS 2.79 4.65 7.71 10.15 0 52.46 EDGE FACE [nm]DEW 0/200 0/200 0/200 0/200 12/200 0/200 CONDENSATION MOUTING 0/2000/200 0/200 0/200  0/200 4/200

Next, all samples of the examples 1 to 4 were determined as good in themounting test. It is thought that this was because the thickness B ofthe water repellent agent 30 on the edge face 27 was smaller than thethickness A of the water repellent agent 30 on the outer circumference26, and the water repellent agent 30 suppressed the prevention of thecrawling of the solder on the edge face 27. In the comparative example1, all samples were determined as good in the mounting test. It isthought that this was because the water repellent agent 30 was notformed on the edge face 27. However, in the comparative example 2, 4samples among 200 samples were determined as bad in the mounting test.It is thought that this was because the thickness B of the waterrepellent agent 30 on the edge face 27 was larger than the thickness Aof the water repellent agent 30 on the outer circumference 26, and thewater repellent agent 30 did not suppress the prevention of the crawlingof the solder on the edge face 27.

(Examples 5 to 8) The multilayer ceramic capacitors were made by thesame processes as those of the examples 1 to 4. The multilayer ceramiccapacitors 100 were fixed to a jig. The regions other than the regionswhere the water repellent agent 30 were to be formed were masked.Silicon rubber was contacted to the surfaces of the multilayer ceramiccapacitors 100. Thus, the water repellent agent 30 was selectivelyformed on the regions which were not masked. In the example 5, thethickness of the water repellent agent 30 on the outer circumference was9.49 nm. And the thickness of the water repellent agent 30 on the edgeface 27 was 3.82 nm. In the example 6, the thickness of the waterrepellent agent 30 on the outer circumference was 22.36 nm. And thethickness of the water repellent agent 30 on the edge face 27 was 5.99nm. In the example 7, the thickness of the water repellent agent 30 onthe outer circumference was 31.14 nm. And the thickness of the waterrepellent agent 30 on the edge face 27 was 8.01 nm. In the example 8,the thickness of the water repellent agent 30 on the outer circumferencewas 50.69 nm. And the thickness of the water repellent agent 30 on theedge face 27 was 11.36 nm. In the comparative example 3, the waterrepellent agent 30 was formed on neither the outer circumference 26 northe edge face 27. In the comparative example 4, the thickness of thewater repellent agent 30 on the outer circumference was 19.91 nm. Andthe thickness of the water repellent agent 30 on the edge face 27 was28.19 nm.

The examples 5 to 8 and the comparative examples 3 and 4 were subjectedto the mounting test and the dew condensation test. Table 2 shows theresults. As shown in Table 2, all samples of the examples 5 to 8 weredetermined as good in the dew condensation test. It is thought that thiswas because the water repellent agent 30 was formed on the outercircumference 26. All samples of the comparative example 4 weredetermined as good in the dew condensation test. It is thought that thiswas because the water repellent agent 30 was formed on the outercircumference 26. However, in the comparative example 3, 12 samplesamong 200 samples were determined as bad in the dew condensation test.It is though that this was because the water repellent agent 30 was notformed on the outer circumference 26.

TABLE 2 EXAMPLE EXAMPLE EXAMPLE EXAMPLE COMPARATIVE COMPARATIVE 5 6 7 8EXAMPLE 3 EXAMPLE 4 THICKNESS 9.49 22.36 31.14 50.69 0 19.91 OF OUTERCIRCUMFERENCE [nm] THICKNESS 3.82 5.99 8.01 11.36 0 28.19 EDGE FACE [nm]DEW 0/200 0/200 0/200 0/200 12/200 0/200 CONDENSATION MOUNTING 0/2000/200 0/200 0/200  0/200 2/200

Next, all samples of the examples 5 to 8 were determined as good in themounting test. It is thought that this was because the thickness B ofthe water repellent agent 30 on the edge face 27 was smaller than thethickness A of the water repellent agent 30 on the outer circumference26, and the water repellent agent 30 suppressed the prevention of thecrawling of the solder on the edge face 27. All samples of thecomparative example 3 were determined as good in the mounting test. Itis thought that this was because the water repellent agent 30 was notformed on the edge face 27. However, in the comparative example 4, twosamples among 200 samples were determined as bad in the mounting test.It is thought that this was because the thickness of the water repellentagent 30 on the edge face 27 was larger than the thickness A of thewater repellent agent 30 on the outer circumference 26, and the waterrepellent agent 30 did not suppress the prevention of the crawling ofthe solder on the edge face 27.

The thickness of the water repellent agent 30 was measured by the XPSdepth analysis. The device used in the XPS depth analysis was QuanteraSXM made by ULVAC PHI. Al Kα (monochrome) was used as an excited X-ray.An analyzed diameter was 100 μm. Electrons/Ar ions were used forelectrostatic charge neutralization. The sputtering rate was 40 cycleper 1 min in 1 cycle at 0.5 kV (0.36 nm/min in a case of SiO₂).

Although the embodiments of the present invention have been described indetail, it is to be understood that the various change, substitutions,and alterations could be made hereto without departing from the spiritand scope of the invention.

What is claimed is:
 1. A ceramic electronic device comprising: amultilayer chip in which each of a plurality of dielectric layers andeach of a plurality of internal electrode layers are alternatelystacked, a main component of the dielectric layers being ceramic, themultilayer chip having a rectangular parallelepiped shape, the pluralityof internal electrode layers being exposed to at least one of a firstend face and a second end face of the multilayer chip, the first endface facing with the second end face; external electrodes provided onthe first end face and the second end face; and a water repellent agentformed on a surface of the external electrodes, wherein a thickness A(>0) of the water repellent agent on at least one of four faces of theexternal electrodes that cover an upper face in a stacking direction, alower face in the stacking direction, and two side faces of themultilayer chip is larger than a thickness B (>0) of the water repellentagent on faces of the external electrodes that cover the first end faceand the second end face.
 2. The ceramic electronic device as claimed inclaim 1, wherein the thickness A is 10 nm or more.
 3. The ceramicelectronic device as claimed in claim 1, wherein the external electrodesinclude a conductive resin layer including a metal component.
 4. Theceramic electronic device as claimed in claim 1, wherein the waterrepellent agent includes at least one of a silicon-based material and afluorine-based material.
 5. A manufacturing method of a ceramicelectronic device comprising: preparing a ceramic electronic devicehaving a multilayer chip, and external electrodes; and forming an waterrepellent agent on a surface of the external electrodes; wherein themultilayer chip has a structure in which each of a plurality ofdielectric layers and each of a plurality of internal electrode layersare alternately stacked, a main component of the dielectric layers beingceramic, the multilayer chip having a rectangular parallelepiped shape,the plurality of internal electrode layers being exposed to at least oneof a first end face and a second end face of the multilayer chip, thefirst end face facing with the second end face, the external electrodesbeing provided on the first end face and the second end face, wherein athickness A (>0) of the water repellent agent on at least one of fourfaces of the external electrodes that cover an upper face in a stackingdirection, a lower face in the stacking direction, and two side faces ofthe multilayer chip is larger than a thickness B (>0) of the waterrepellent agent on faces of the external electrodes that cover the firstend face and the second end face.
 6. The method as claimed in claim 5,wherein the water repellent agent is formed by contacting silicon rubberheated to 120 degrees C. or more to the four faces or contactingfluorine rubber heated to 150 degrees C. or more to the four faces.